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Chemists at the University of Graz in Austria have invented a way of converting fluoroform, a harmful waste gas produced from the chemical production of Teflon, into eflornithine, a drug used to treat sleeping sickness, using a 3D printed stainless steel continuous flow reactor.

Sleeping sickness, AKA African trypanosomiasis, has a mortality rate close to 100% when untreated. Estimates are that 50,000 to 500,000 people die from this disease every year.

The continuous flow process is especially valuable because it usefully converts the fluoroform, which would otherwise have been burned off, without any waste products between the steps of the chemical reaction.

Diagram and CAD image of the reactor. Image via Karl-Franzens-University of Graz.

The chemical reaction

Fluoroform has a large global warming potential (14,800 times higher than carbon dioxide over a 100-year period), meaning that its discharge into the environment is restricted by the Kyoto Protocol.

While burning off the fluoroform prevents it from escaping into the atmosphere, doing so produces Carbon Dioxide emissions. Instead, “we use it to make eflornithine, a major sleeping sickness drug, which has been added to the Essential Medicines list by the World Health Organization (WHO),” explained project leader Dr C. Oliver Kappe.

3D printing allowed the scientists freedom of material and freedom of shape. Freedom of material was important since more common poly(dimethylsiloxane) (PDMS) reactors, which were fabricated using soft lithography, have a low chemical compatibility with organic solvents.
Freedom of shape not only ensured that multiple reactions were combined into one process, but it also gave the scientists maximum control over the temperature, pressure, mixing structures, mixing points, flow paths, and residence volumes in the reaction.

A virtual model was initially created using 3D graphics software, with custom features such as a channels diameter of 0.8 mm, and a meandering channel pathway, together with minimized distortion from manufacturing stresses.

To fabricate the continuous flow reactor, an EOS M 280 SLM 3D printer was used by manufacturers Anton Paar, with 316 L stainless steel powder with a median particle size of 43.5 μm as feedstock. The printing process took 14 hours to complete, during which build chamber was filled with nitrogen to prevent the components from reacting to Oxygen.

“With 3D printing, flow reactors of any complexity can be produced, whereas conventional production methods limit this considerably,” said Kappe “This also means a huge cost saving.”